Periodontitis: from Infection to Inflammation

Mycobacterium tuberculosis : a new hitchhiker in the etiopathogenesis of periodontitis

Periodontitis, a chronic inflammatory disease of the gums affects both the ligament and alveolar bone. A severe form of periodontal disease affects a strikingly high number of one billion adults globally. The disease permutes both the soft and hard tissues of the oral cavity leading to localized and systemic diseases. Periodontitis has a deleterious impact on systemic health causing diabetes, cardiovascular diseases (CVD), and other disease. The cause of the enhanced inflammatory process is due to dysbiosis and an unregulated immune response. Innate immune response and T cells trigger uninhibited cytokine release causing an unwarranted inflammatory response. The RANK- RANKL interaction between osteoblasts, immune cells, and progenitor osteoclasts results in the maturation of osteoclasts, which promote bone resorption. It is well established that dysbiosis of the oral cavity has been implicated in periodontitis. But emerging reports suggest that the pulmonary pathogen, Mycobacterium tuberculosis (Mtb), causes extrapulmonary diseases such as periodontitis. Many clinical case reports advocate the involvement of Mtb in periodontitis, which poses a threat with the surge of tuberculosis in HIV and other immunocompromised individuals. Fostering a better understanding of the mechanism, causative agents and control on inflammatory response is imperative in the prevention and treatment of periodontitis.

Confounding in observational studies evaluating the association between Alzheimer's disease and periodontal disease: A systematic review

Background

Studies investigating the association between periodontitis and Alzheimer's disease (AD) suggested indirect (periodontitis would increase the circulation of inflammation-inducible molecules) and direct (periodontopathogens might colonize brains affected by Alzheimer's disease) pathways. While there seems to be a positive relationship between periodontitis and AD, concerns have been raised about the role of confounding.

Aim

To systematically review the literature to assess confounding and their level of heterogeneity in the association between periodontitis and AD. Also, to examine data reporting and interpretation regarding confounding bias.

Methods

This review followed the PRISMA guidelines and was registered within PROSPERO. Electronic searches were performed in seven main databases and three others to capture the "grey literature". The PECO strategy was used to identify observational studies (cross-sectional, case-control, or cohort studies) assessing the association between periodontal disease and AD without restricting publication language and year. Critical appraisal was performed according to the Joanna Briggs Institute guidelines. Confounders were evaluated following a two-step approach.

Results

A total of 3255 studies were found, of which 18 (13 case-control, four cross-sectional, and one cohort) met the eligibility criteria. Participants with AD were 1399 (mean age 64 ± 9 to 84.8 ± 5.6 years), whereas those without AD were 1730 (mean age 62.6 ± 7.1 to 81.4 ± 4.6). Female patients composed most of the sample for both groups. The confounding variables "age" and "sex" were present in all studies. Four studies used the 2017 AAP/EFP periodontal classification. Most studies had a low risk of bias. Fifty percent of the articles did not consider confounding; variation in the adjustment approaches was observed. Additionally, 62% of the studies did not mention bias, and 40% did not discuss any limitations about confounders.

Conclusions

Given the study's limitations, caution must be taken to properly interpret the association between periodontitis and AD.Registration: CRD42022293884.

Effect of Smoking Exposure on Nonsurgical Periodontal Therapy: 1-Year Follow-up

This study investigated the influence of different levels of exposure to smoking on periodontal healing for 12 mo after nonsurgical periodontal therapy and supportive periodontal care every third month. Eighty smokers willing to quit smoking and with periodontitis were included. Participants were offered an individualized voluntary smoking cessation program. Data collection included questionnaires and a full-mouth periodontal examination. Group-based trajectory modeling was used to model smoking trajectories over the follow-up. The effect of smoking trajectory on periodontal parameters over time was estimated with mixed effects modeling. Three smoking patterns were identified: light smokers/quitters (n = 46), moderate smokers (n = 17), and heavy smokers (n = 17). For the periodontal data, the first factor, moderate periodontitis, included the number of sites with clinical attachment levels (CALs) of 4, 5, 6, and 7 mm; periodontal pocket depths (PPDs) of 4, 5, and 6 mm; and bleeding on probing. The second factor, severe periodontitis, consisted of the number of sites with a CAL ≥8 mm and PPD ≥7 mm. Heavy smokers commenced with a higher average CAL of 1.1 mm and 10 more sites with severe periodontitis than light smokers/quitters. While light smokers/quitters and moderate smokers obtained an average improvement of 0.6-mm PPD and 0.7-mm CAL, respectively, heavy smokers experienced 0.5-mm attachment loss. Heavy smokers had only a 50% reduction in the number of sites with moderate periodontitis when compared with light smokers/quitters and moderate smokers. While most participants benefited from nonsurgical periodontal therapy with results affected in a dose-response manner, the therapy had no effect on severe periodontitis among heavy smokers. Smoking cessation should be part of periodontal therapy; otherwise, limited benefits would be observed among heavy smokers, hindering the effect of treatment.

The role of cigarette smoking in periodontal disease and treatment outcomes of dental implant therapy

Tobacco smoking has been implicated in periodontal pathology through various mechanisms, including perturbations of the inflammatory and host responses to putative periodontal pathogens, alterations in the subgingival microbial communities, and a compromised healing potential of the tissues leading to imbalance of tissue homeostasis. This review provides the evidence for the relationship between cigarette smoking and periodontal disease in an attempt to explain possible mechanisms of how tobacco smoking may exert its negative effects on the periodontal tissues via systemic and localized pathways. Early and more recent studies explore cigarette smoking-induced changes in periodontal clinical indices; in subgingival microbial flora by employing traditional detection methods for selected microorganisms, in addition to modern techniques such as deep sequencing and bioinformatics analyses that are able to fully characterize the microbial communities; and in inflammatory and immune responses critically appraising study limitations and differences in study protocol designs. Periodontal treatment outcomes and implant therapy outcomes are reviewed in an attempt to shed light on possible mechanisms for the inferior treatment outcome noted in smokers. The potential harmful effects of passive smoking are also reviewed, providing evidence for the advantages of smoking cessation. Quitting cigarette smoking should be recommended by the dentist, and effort should be made to inform smokers about the negative effects of smoking on the periodontal status and implant therapy outcomes.

Clinical Effects of Locally Delivered Lactobacillus reuteri as Adjunctive Therapy in Patients with Periodontitis: A Split-Mouth Study

Different methods and products have been investigated as measures of adjunctive therapy to scaling and root planing (SRP). Probiotic use has gained interest for this particular application, especially Lactobacillus spp. This split-mouth interventional prospective study aimed to evaluate the clinical effects of L. reuteri DSM 17938 with local application in periodontal pockets of severe periodontitis patients. The study was conducted on 40 subjects with stage 3–4 periodontitis who, based on a split-mouth model, followed SRP and SRP + L. reuteri solution in five weekly sessions. Probing depth (PD), clinical attachment loss (CAL), and bleeding on probing (BOP) were assessed at baseline and at three months after probiotic treatment completion. Both SRP and SRP + L. reuteri generated significant improvements of all three clinical parameters, but the changes were significantly better for SRP + L. reuteri treated sites. Therefore, we can conclude that adjunctive therapy with L. reuteri DSM 17938 could represent an interesting treatment option, particularly for severe periodontitis cases.

Periodontal Inflammation and Systemic Diseases: An Overview

Periodontitis is a common inflammatory disease of infectious origins that often evolves into a chronic condition. Aside from its importance as a stomatologic ailment, chronic periodontitis has gained relevance since it has been shown that it can develop into a systemic condition characterized by unresolved hyper-inflammation, disruption of the innate and adaptive immune system, dysbiosis of the oral, gut and other location's microbiota and other system-wide alterations that may cause, coexist or aggravate other health issues associated to elevated morbi-mortality. The relationships between the infectious, immune, inflammatory, and systemic features of periodontitis and its many related diseases are far from being fully understood and are indeed still debated. However, to date, a large body of evidence on the different biological, clinical, and policy-enabling sources of information, is available. The aim of the present work is to summarize many of these sources of information and contextualize them under a systemic inflammation framework that may set the basis to an integral vision, useful for basic, clinical, and therapeutic goals.

Cytokine profiles and the dynamic of gingivitis development in humans

AIM

To investigate the relationship between cytokine profiles and "fast" and "slow" patterns of gingival inflammation development.

MATERIALS AND METHODS

Forty-two adults participated in an experimental gingivitis study, comprising a 2-week hygiene phase (clinical examination and professional cleaning); a 3-week induction phase (absence of oral hygiene); and a 2-week resolution phase (re-establishment of oral hygiene). Plaque and gingival inflammation scores were assessed. Interferon-gamma (IFN-γ), interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, and tumour necrosis factor-alpha (TNF-α) from gingival crevicular fluid were collected and measured by multiplex ELISA. Group-based-trajectory-modelling (GBTM) was used to model cytokine profiles over the induction phase. The effect of gingival inflammation on cytokine levels over time was estimated with mixed-effects modelling.

RESULTS

GBTM analysis revealed two cytokine profiles, "non-organized response" (IL-4, IL-6, IL-8, IL-12, and IL-13) and "organized response" (IL-2, IL-10, and TNF-α). Among the "slow" responders, neither cytokine profile was associated with gingivitis. In contrast, a "fast" response was associated with a higher "non-organized response" factor (coef. 0.14) and a lower "organized response" factor (coef. -0.03).

CONCLUSION

A "fast" gingivitis development was associated with a higher "non-organized response" and a lower "organized response", which may elucidate the role of individual variability in gingivitis susceptibility.

Use of air polishing for supra- and subgingival biofilm removal for treatment of residual periodontal pockets and supportive periodontal care: a systematic review

AIM

To systematically review the literature to compare the efficacy of air polishing to hand or ultrasonic instrumentation to reduce periodontal inflammation during treatment of residual pockets or supportive periodontal care.

METHODS

Electronic searches were performed in five different databases, and two databases were used to capture the "grey literature partially." Clinical trials that compared the use of an air-polishing device to either conventional scaling and root planing (hand and/or ultrasonic instrumentation) or no treatment during periodontal therapy were included without restriction of year and publication status. The Joanna Briggs Institute instrument for clinical trials was used to appraise the studies critically. The results were submitted to qualitative descriptive analysis. The systematic review protocol was registered in PROSPERO (CRD420220156176).

RESULTS

Electronic searches found 1100 hits published between 2008 and 2019. Thirteen studies were included in the review, out of which four had a follow-up longer than 180 days. Results indicated no differences between the efficacy of air polishing and hand or ultrasonic instruments to reduce periodontal inflammation.

CONCLUSIONS

Our findings suggest that there is no difference in the efficacy of air polishing and hand or ultrasonic instrumentation to control biofilm and reduce periodontal inflammation. However, these findings must be carefully interpreted owing to methodological issues, including a short follow-up, and a potential conflict of interest related to industry funding.

CLINICAL RELEVANCE

Air polishing for biofilm control may be used as an alternative to hand and ultrasonic instrumentation to reduce periodontal inflammation during treatment of residual pockets or supportive periodontal care.

Association of Polymorphism in IL-18 Gene with Periodontitis in Uyghur Adults in Xinjiang and Evidence from Six Case-Control Studies with a Comprehensive Analysis

AIM

The aim of the study was to evaluate the association of IL-18 137 G > C, 607 C > A gene polymorphism in Uyghur population with chronic periodontitis (CP) and combine the results with the meta-analysis.

METHODS

In a case-control study, 200 cases with CP and 100 healthy controls were recruited; IL-18 137 G > C, 607 C > A genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In the meta-analysis, we used electronic databases, including CNKI, Wan Fang, PubMed, EMBASE databases etc.to obtain relevant research published through June 2020. Studies were considered eligible if odds ratios (ORs) and 95% confidence intervals (95% CI) were provided or calculated from the given data. The size of the combined effect was calculated using STATA 15.0.

RESULTS

Our study revealed significant association between CP and IL-18 137 G > C (P = .045, OR = 1.67), 607 C > A (P = .045, OR = 1.67). The overall meta-analysis revealed significant associations between IL-18 137 G > C polymorphism and CP risk in Allele, dominant, co-dominant and recessive genetic models. The subgroup analysis also showed a significant association between the IL-18 137 G > C and risk for periodontitis and aggressive periodontitis in the Asian (GC+ CC VS. GG: P = .047, OR = 1.64,95%CI = 1.01-2.68).

CONCLUSIONS

IL-18 137 G > C, 607 C > A could be associated with susceptibility to periodontitis in Uyghur population. Further case-control of candidate genes studies targeting larger sample sizes and different ethnic groups are needed to arrive more accurate conclusions.

The Controlled Direct Effect of Early-Life Socioeconomic Position on Periodontitis in a Birth Cohort

This study used data from the 1982 Pelotas Birth Cohort Study, Brazil, to estimate the controlled direct effect of early-life socioeconomic position (SEP) on periodontitis at age 31 years, controlling for adulthood income and education, smoking, and dental hygiene. Sex was included as a covariate. Early-life SEP was measured at participant birth based on income, health services payment mode, maternal education, height, and skin color (lower versus middle/higher SEP). Periodontitis was assessed through clinical examination at age 31 years (healthy, mild periodontitis, or moderate-to-severe disease). Adulthood behaviors (smoking, dental hygiene) were the mediators, and adulthood SEP (education and income) represented the exposure-induced mediator-outcome confounders. A regression-based approach was used to assess the controlled direct effect of early-life SEP on periodontitis. Multinomial regression models were used to estimate risk ratios and their 95% confidence intervals. The prevalences of mild and moderate-to-severe periodontitis were 23.0% and 14.3%, respectively (n = 539). Individuals from the lowest early-life SEP had a higher risk of moderate-to-severe periodontitis controlled for mediators and exposure-induced mediator-outcome confounders: risk ratio = 1.85 (95% confidence interval: 1.06, 3.24), E value 3.1. We found that early-life SEP was associated with the development of periodontitis in adulthood that was not mediated by adulthood SEP and behaviors.

Salivary levels of MPO, MMP-8 and TIMP-1 are associated with gingival inflammation response patterns during experimental gingivitis

AIM

This study aimed to investigate the association between salivary levels of myeloperoxidase (MPO), neutrophil elastase (NE), soluble urokinase-type plasminogen activator receptor (suPAR), matrix metalloproteinase (MMP)-8 and tissue inhibitor of matrix metalloproteinases (TIMP)-1 and gingival inflammation development during an experimental gingivitis study.

METHODS

A three-week experimental gingivitis study was conducted. Clinical recordings of dental plaque biofilm (Modified Quigley Hein Plaque Index, TQHPI) and gingival inflammation (Modified Gingival Index, MGI) were made at specific time points for each of the 42 participants. Salivary levels of MPO, NE, suPAR, MMP-8 and TIMP-1 at the same time points were measured using distinct immunoassays. For data analysis growth curve modelling was employed to account for the time-varying outcome (MGI score) and the time-varying covariates (salivary marker levels, and TQHPI score). Analyses were stratified according to the MGI-score trajectory groups previously identified as 'fast', respectively 'slow' responders.

RESULTS

Overall, higher MGI scores were statistically significantly positively associated with higher levels of MPO, MMP-8 and TIMP-1. Stratified analysis according to inflammation development trajectory group revealed higher levels of salivary MPO, MMP-8 and MMP-8/TIMP-1 ratio among the 'fast' responders than among 'slow' responders. None of the investigated salivary protein markers was associated with a 'slow' inflammation development response.

CONCLUSIONS

Salivary levels of MPO, MMP-8 and TIMP-1 were associated with the extent and severity of gingival inflammation. While the 'fast' gingival inflammation response was associated with increased levels of MPO, MMP-8 and MMP-8/TIMP-1 ratio, the 'slow' response was not associated with any of the salivary protein markers investigated in this study. Neutrophil activity seems to orchestrate a 'fast' gingival inflammatory response among participants previously primed to gingival inflammation.

Systematic review and meta-analysis of double-blind, placebo-controlled, randomized clinical trials using probiotics in chronic periodontitis

AIM

The aim of the present study was to evaluate the efficacy of probiotics as an adjunct to scaling and root planning (SRP) in the treatment of chronic periodontitis (CP).

METHODS

The focused question of the study was: Does adjunctive use of probiotics yield better clinical periodontal outcomes compared to placebo/no treatment group in the treatment of CP? Electronic and manual literature searches were conducted up to December 2017 using the following databases: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register. Forest plots were computed reporting weighted mean difference (WMD) of outcomes and 95% confidence intervals (CI).

RESULTS

Seven clinical studies were included. Four studies showed additional benefits in reducing periodontal probing depth (PPD) and gaining clinical attachment level (CAL), whereas, three studies showed comparable clinical periodontal outcomes between probiotics and SRP/placebo. Significant heterogeneity was observed for PPD reduction and CAL gain. The overall mean difference for CAL gain between probiotics and placebo/SRP was significant (WMD = 1.41, 95% CI = 0.15-2.67, P = .028) at follow up.

CONCLUSION

Adjunctive probiotics could result in additional benefits in CAL gain in CP. Nevertheless, further high-quality randomized clinical trials with microbiological outcomes are warranted to obtain strong conclusions in this regard.